U.S. patent application number 12/021973 was filed with the patent office on 2009-07-30 for operating a rotary mower using gearbox temperature.
Invention is credited to Don Assie, Blake Neudorf, Cam Wilson.
Application Number | 20090188224 12/021973 |
Document ID | / |
Family ID | 40897830 |
Filed Date | 2009-07-30 |
United States Patent
Application |
20090188224 |
Kind Code |
A1 |
Assie; Don ; et al. |
July 30, 2009 |
OPERATING A ROTARY MOWER USING GEARBOX TEMPERATURE
Abstract
With a rotary mower having a driveline including a plurality of
gearboxes, a method of operating the rotary mower includes
providing a sensor operative to measure a temperature of each
gearbox in the driveline; monitoring the temperature in each gear
box; and operating the mower to maintain the temperature of each
gearbox at a level below a maximum acceptable temperature.
Inventors: |
Assie; Don; (Vonda, CA)
; Neudorf; Blake; (Vonda, CA) ; Wilson; Cam;
(Vonda, CA) |
Correspondence
Address: |
DICKE, BILLIG & CZAJA
FIFTH STREET TOWERS, 100 SOUTH FIFTH STREET, SUITE 2250
MINNEAPOLIS
MN
55402
US
|
Family ID: |
40897830 |
Appl. No.: |
12/021973 |
Filed: |
January 29, 2008 |
Current U.S.
Class: |
56/7 ; 56/10.8;
56/364; 701/29.5 |
Current CPC
Class: |
A01D 75/182
20130101 |
Class at
Publication: |
56/7 ; 56/364;
56/10.8; 701/30 |
International
Class: |
A01D 34/66 20060101
A01D034/66; A01D 34/74 20060101 A01D034/74; A01D 69/02 20060101
A01D069/02; G01M 19/00 20060101 G01M019/00 |
Claims
1. A method of operating a rotary mower, the rotary mower
comprising a driveline including a main drive shaft connecting a
tractor power take off to a middle gearbox, wherein the middle
gearbox drives a middle blade and the middle gearbox drives right
and left gearboxes and the middle gearbox is rated to transfer a
total power requirement therethrough, and the right and left
gearboxes are rated to transfer a partial power requirement
therethrough, and wherein the partial power requirement is less
than one half of the total power requirement, the method
comprising: providing a sensor operative to measure a temperature
of each gearbox in the driveline; monitoring the temperature in
each gearbox; and operating the mower to maintain the temperature
of each gearbox at a level below a maximum acceptable
temperature.
2. The method of claim 1 further comprising providing an alarm
operative to alert an operator that the temperature of a gearbox
exceeds the maximum acceptable temperature.
3. The method of claim 1 wherein operating the mower to maintain
the temperature of each gearbox at a level below a maximum
acceptable temperature comprises, when the temperature of a gearbox
exceeds the maximum acceptable temperature, one of reducing a
travel speed of the mower and increasing a cutting height of the
mower.
4. (canceled)
5. (canceled)
6. A method of operating a rotary mower, the rotary mower
comprising a main drive shaft connecting a tractor power take off
to a middle gearbox, wherein the middle gearbox drives a middle
blade and the middle gearbox drives right and left gearboxes and
the middle gearbox is rated to transfer a total power requirement
therethrough, and the right and left gearboxes are rated to
transfer a partial power requirement therethrough, and wherein the
partial power requirement is less than one half of the total power
requirement, the method comprising: providing a sensor operative to
measure a temperature of each gearbox; monitoring the temperature
in each gear box; and one of reducing a travel speed of the mower
and increasing a cutting height of the mower when the temperature
in one of the gearboxes increases to a maximum acceptable
temperature.
7. The method of claim 6 further comprising providing an alarm
operative to alert an operator that the temperature of a gearbox
exceeds the maximum acceptable temperature.
Description
[0001] This Utility patent application claims priority to Canadian
Patent Application No. ______ filed on Dec. 18, 2007, which is
incorporated herein by reference.
BACKGROUND
[0002] This invention is in the field of rotary mowers and in
particular is concerned with an improved method of operating such a
mower using conditions sensed in the gearbox, such as temperature,
as a guide.
[0003] A typical rotary mower includes one or more rotating blade
assemblies mounted for movement along the ground to cut vegetation.
The blade assemblies rotate about vertical axes, and are driven
from the power take off (pto) shaft of a towing tractor that spins
about a generally horizontal axis. Thus a gear box is required at
the top of each blade assembly to convert the rotation about the
horizontal axis to rotation about the vertical axis. A drive shaft
connects the pto shaft to a first gear box on the mower, which is
in turn connected to other drive shafts connecting further
downstream gearboxes to form a driveline comprising numerous
gearboxes and drive shafts to connect each blade assembly to the
pto shaft.
[0004] The first gearbox must be designed to transmit all the power
being used by all the blade assemblies of the mower, but gear boxes
farther downstream in the driveline transmit less power as the
drive shafts split off to each blade assembly, and the gearbox at
the top of each blade assembly is only required to transmit the
power required by that single assembly. Thus the first gearbox on a
mower with three equal sized blade assemblies, may be designed and
rated to transmit 90 horsepower (HP) while the gearboxes at the top
of the blade assemblies are only required and rated to transmit 30
HP to the blade assembly they are driving.
[0005] The power output at the towing tractor's pto shaft should be
selected to substantially correspond to the power rating of the
mower. The power drawn by the mower and transmitted through the
driveline varies with the speed of travel of the mower and the
amount of vegetation being cut. The operator generally balances
these factors when operating the mower to substantially utilize the
power available. The operator will watch the engine speed and when
the engine begins to lug down, such as where the vegetation is high
and dense, the operator will slow the travel speed, and when the
vegetation gets thinner, the operator will increase the travel
speed. The operator may also reduce the width of vegetation cut to
reduce the power requirements of the mower.
[0006] As power is transmitted through the gearboxes, the meshing
gears and rotating bearings generate heat, and the gear boxes are
generally designed to operate at some elevated design temperature
when the maximum rated power is being transmitted. Generally,
operating above the design temperature can lead to failure of seals
and loss of lubricating oil leading to failure of the gearbox.
Elevated temperatures may also decrease the effectiveness of
lubricating oil, and lead to failure of the meshing gears.
[0007] Elevated temperatures generally indicate some wear or
pending failure in a gearbox. Exceeding the power rating of a
gearbox can also cause the gearbox to overheat. Monitoring
conditions such as temperature and vibration is known in various
rotating equipment to detect defects. U.S. Pat. No. 6,425,293 to
Woodruffe et al. for example discloses a sensor plug for sensing
operating conditions in a gearbox. Woodruffe states that excessive
vibration in the gearbox is an indication of malfunction, such as
broken gear teeth, worn bearings, misaligned shafts and the like,
which can lead to machine failure. Woodruffe also discusses
monitoring gearbox temperatures to detect over-heating of bearings
and gears, and suggests cooling the gearbox when elevated
temperatures are detected by fans, spraying cooling liquid,
connecting a climate control unit, and like measures.
SUMMARY
[0008] It is an object of the present invention to provide a method
of operating a rotary mower that overcomes problems in the prior
art.
[0009] The present invention provides a method of operating a
rotary mower where the rotary mower comprises a driveline including
a plurality of gearboxes. The method comprises providing a sensor
operative to measure a temperature of each gearbox in the
driveline; monitoring the temperature in each gear box; operating
the mower to maintain the temperature of each gearbox at a level
below a maximum acceptable temperature.
[0010] In many rotating drive applications it is not practical to
reduce the power transmitted through the driveline. The load on
many rotating machines is substantially constant, and the machine
is operated at a set power level to accomplish the task at
hand.
[0011] Operating a rotary mower, however, is an operation where the
amount of power being transferred through the mower driveline
varies considerably with ground speed and the amount of vegetation
being cut. The mower operator knows when the power drawn by the
mower exceeds the power available at the tractor pto because the
engine speed will drop, and either the sound of the engine or a
look at the tachometer will advise the operator, who can then
reduce the load by slowing down ground speed or cutting a narrower
swath. Although it is generally desired to conduct a mowing
operation at a consistent cutting height, in some conditions the
operator may reduce power requirements by raising the mower to cut
less vegetation. The operator may then be required to make a second
pass over the same ground with the mower set at the desired height.
The operator in some manner is then able to match the varying power
requirements of the mower to the substantially constant power
available from the tractor.
[0012] Problems arise where the power available at the tractor pto
substantially exceeds the power rating of the mower. The operator
then has no readily available indicator of whether the power being
transmitted through the mower driveline exceeds the rated power of
the driveline, and the gearboxes can overheat and be damaged.
Weather also can significantly affect the temperature of a gearbox.
When the ambient temperature is very hot, the gear boxes may exceed
the design operating temperature even when the power being
transmitted is at or below the rated power of the gearbox, leading
to failure due to overheating.
[0013] A further problem arises when an operator reduces the load
by reducing the width of cut. A mower might have three equal sized
blade assemblies mounted on the left, middle, and right portions of
the mower, and be designed to have a load of 90 HP. Thus the first
gearbox on the mower is connected to the tractor pto and is rated
to transmit 90 horsepower (HP). This first 90 HP gearbox is often
mounted on top of the middle blade assembly and has an output shaft
extending down to drive the middle blade assembly, and right and
left output shafts connected to right and left gear boxes at the
top of the right and left blade assemblies. The right and left
gearboxes are only required and rated to transmit 30 HP to the
corresponding right and left blade assemblies.
[0014] Thus when the mower is cutting full width each blade
assembly is drawing about an equal amount of power. When the
vegetation gets more dense, and the load increase drawing down the
tractor engine speed, the operator may move toward the side that
has been cut on a previous pass of the mower to reduce the width of
cut. Thus the load on the left blade assembly will be reduced, and
the engine speed will pick up and the operator will proceed with
mowing, the tractor again delivering 90 HP to the mower. The
distribution of the power is however now unbalanced--the left blade
assembly may only be drawing 10 HP, while the middle and right
blade assemblies are each drawing 40 HP. This may not be
problematic for the 90 HP gearbox driving the middle blade, but the
gearbox driving the right blade is transmitting 40 HP instead of
its rated 30 HP. The risk of overheating and damage is
substantially increased where the power transmitted through the
gearbox exceeds the rated power.
[0015] Even when cutting a full width with the mower, it is not
uncommon for the density of the vegetation to vary across the
width, causing unbalanced loading of the gearboxes on the mower.
The total power requirement will be at or under the rated power so
that the operator will be unaware of the condition. By indicating
the temperature of each gearbox to the operator, the operator can
take whatever remedial action is required to ensure that one of the
gearboxes is not experiencing an excessive temperature indicating
that the gearbox is overloaded and exceeding its power rating.
[0016] Thus gearbox temperatures can rise because power
requirements and ambient temperatures combine to raise the
temperature in a gearbox that is structurally sound, or because the
gearbox is damaged.
[0017] Regardless of the reason for the rise in gearbox
temperature, there is a temperature threshold where the gearbox
seals and the lubricating oil will no longer stand up to the
temperature, and will be damaged. Thus advising the operator of the
gearbox temperature in a mower can allow the operator to take steps
to prolong the life of a damaged gearbox while provision is being
made to replace or repair the gearbox, or to protect the gearbox
from damage when conditions cause a sound gearbox to overheat. For
example it may be that extremely high ambient temperatures are
causing overheating without drawing down the tractor engine speed.
The operator can reduce travel speed and thus power consumption to
reduce the temperature of the gear box until ambient temperature
falls, and normal operation can resume. Similarly where uneven
vegetation is causing excessive loads in one gearbox while the
total load is under the rated load, the operator will be made aware
of the condition, and can slow the travel speed.
[0018] Where the gearbox temperature rises because the gearbox is
damaged or worn, the operator will be warned of the condition. For
example it may be that a seal has failed, and thus the operator may
be able to continue operations by periodically adding lubricating
oil to the gearbox to prevent damage to the gears until a
convenient time for making a proper repair. Costly replacement and
repair of the gears may be avoided.
[0019] The operator is provided with constant temperature
monitoring of each gearbox using an actual temperature readout, and
an audible or visible alarm may also be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] While the invention is claimed in the concluding portions
hereof, preferred embodiments are provided in the accompanying
detailed description which may be best understood in conjunction
with the accompanying diagrams where like parts in each of the
several diagrams are labeled with like numbers, and where:
[0021] FIG. 1 is a schematic top view of a rotary mower adapted for
practicing a method of the present invention;
[0022] FIG. 2 is a schematic front view of a temperature gauge set
for use with the mower of FIG. 1;
[0023] FIG. 3 is a schematic top view of the rotary mower of FIG. 1
operating in a full width cut position and a reduced width cut
position;
[0024] FIG. 4 is a schematic side view of the rotary mower of FIG.
1 operating in a low cutting position and a raised cutting
position;
[0025] FIG. 5 is a schematic side view of the a gearbox of the
rotary mower of FIG. 1 showing a leaking seal.
DETAILED DESCRIPTION
[0026] FIG. 1 schematically illustrates a rotary mower 1 for use
with the method of the present invention. The rotary mower
comprises three equal sized blade assemblies 3 mounted on the left,
middle, and right portions of the mower 1, and a driveline
including a plurality of gearboxes 5. The middle gearbox 5M is
connected to the pto shaft 7 of the towing tractor 9. The gearbox
5M is mounted on top of the middle blade assembly 3M and has an
output shaft (not shown) extending down to drive the middle blade
assembly 3M, and right and left output shafts 11R, 11L connected to
right and left gear boxes 5R, 5L at the top of the right and left
blade assemblies 3R, 3L.
[0027] Temperature sensors 13 are provided in each gearbox 5 and
are operative to measure a temperature of each gearbox 5 and are
connected to indicate the temperatures on a gauge set 15, such as
is illustrated in FIG. 2, located where the operator of the tractor
9 can monitor the temperatures TR, TM, TL in each gear box 5R, 5M,
5L. The operator can then operate the mower to maintain the
temperature of each gearbox 5 at a level below a maximum acceptable
temperature for the gearbox 5 being monitored. An alarm 17 is
operative to alert the operator, with an audible or visible alarm
signal, that the temperature of a gearbox 5 exceeds the maximum
acceptable temperature.
[0028] By monitoring the temperature of the gear boxes 5, the
operator can operate the mower 1 to maintain the temperature of
each gearbox 5 at a level below a maximum acceptable temperature.
When the temperature of a gearbox 5 exceeds the maximum acceptable
temperature, the operator can reduce the travel speed of the mower
1 and monitor the temperature to see if it falls to an acceptable
level.
[0029] Similarly in some conditions the operator may be able to
reduce a width of cut of the mower 1 as illustrated in FIG. 3 by
moving from the full width cutting position 1B to the partial
cutting width position 1A. By reducing the width of cut as
illustrated, the power transmitted through gearbox 5L is reduced,
since the blade assembly driven by the gearbox 5L is passing over a
previously cut strip of vegetation 21 instead of passing over the
uncut vegetation 23. The blade assembly driven by the right gearbox
5R however is passing over the same uncut vegetation 23 in both
positions 1A and 1B, and so reducing the width of cut as
illustrated will not reduce power requirements through gearbox 5R.
The gauge set 15 will indicate to the operator a lower temperature
TL in gearbox 5L, but no change in the temperature TR of the
gearbox 5R. With reduced load on gearbox 5L, there may in fact be
an increase in the temperature of the gearbox 5R if the power not
required by gearbox 5L is drawn through gearbox 5R.
[0030] As illustrated in FIG. 4 the operator may reduce power
requirements to lower gearbox temperatures by raising the mower 1
from position 1AA to position 1BB to cut less vegetation. The
operator may then be required to make a second pass over the same
ground with the mower 1 set at the desired height.
[0031] In any event, the operator is able to monitor each
temperature and operate to maintain all the gearbox temperatures at
an acceptable level. Where the operator detects that a gearbox seal
is leaking lubricating oil 31, as illustrated in FIG. 5, the
operator can periodically add lubricating oil to the gearbox
through the filler port 33 to maintain the temperature of the gear
box 5 at an acceptable level. The operator can perform preventive
maintenance to correct worn or improperly adjusted gearbox
components when that is the cause of the increased temperature.
[0032] It is contemplated that the operator will be able in
numerous other similar ways to keep the mower operating in at least
a somewhat satisfactory manner while avoiding incurring further
damage to a damaged gearbox, or in some situations stop the mowing
operation, and thus avoid costly repairs and downtime.
[0033] The foregoing is considered as illustrative only of the
principles of the invention. Further, since numerous changes and
modifications will readily occur to those skilled in the art, it is
not desired to limit the invention to the exact construction and
operation shown and described, and accordingly, all such suitable
changes or modifications in structure or operation which may be
resorted to are intended to fall within the scope of the claimed
invention.
* * * * *